A diagnosis of depression includes heterogeneity in etiology, severity of illness, symptom patterns, timing of episodes, treatment, and behavioral functioning. Data in the NIMH longitudinal study of families of affectively ill and well parents make it possible to examine differences within maternal depression and to relate them to child functioning. Mother and child were observed in semi-naturalistic settings. Unipolar depressed mothers were most likely to interact with their children with sustained bouts of negative affect. Patterns of maternal affect were very stable over the two-week period in which they were observed. Significant correlations between levels of negative affect exhibited by mother and child indicate an important synchrony. Bouts of negative affect were correlated only between unipolar depressed or severely depressed mothers and their daughters.